Known methods and apparatus for abrading tire tread compounds or other types of rubber compounds, generally employ a moving abrasive surface. A sample of the compound is engaged with the moving abrasive surface to be abraded. The amount of material abraded from the sample is then measured to predict the wear rate, wear resistance and/or abrasion resistance of the tire tread compound under actual tire wear, or other abrading conditions.
One problem with known abrading methods and apparatus is that abrasion data is provided to predict tread wear at one level, or an average level of abrasion severity. However, for some tire tread compounds, the relative tread wear characteristics may vary dramatically at different levels of abrasion severity. For example, some tire tread compounds demonstrate high tread wear capabilities at low severity levels of abrasion, while demonstrating very poor tread wear capabilities at high severity levels of abrasion. As a result, known abrading apparatus and methods that abrade at only one level, or an average level of abrasion severity, frequently provide misleading abrasion data.
For example, if such an apparatus or method is used to test a tire tread compound at a low level of abrasion severity, it may indicate excellent tread performance while, in fact, at high severity levels of abrasion the same compound may provide very poor tread performance. If such a tire tread compound were then used to make a tire and subjected to high severity abrasion, such as a performance car tire, the tire would likely exhibit a high wear rate and/or develop an irregular wear pattern.
One problem with tire tread compounds that exhibit widely different wear rate characteristics at different levels of abrasion severity, is that tires made from such compounds frequently develop irregular wear patterns. It has been determined that irregular wear is often caused by the uneven distribution of stress in the tread of the tire. If the tire tread compound exhibits low abrasion resistance at high severity levels of abrasion, then the sections of the tire subjected to the higher levels of severity or stress will wear faster than the other sections of the tire. As a result, such tires frequently develop irregular wear patterns that substantially decrease the life of the tire.
Therefore, it can be critical to test the abrasion characteristics of tire tread compounds at both high and low severity levels of abrasion. Because known methods and apparatus have not been used to perform this function, such compounds are usually tested by actual tire tests on road vehicles under both high and low severity abrasion conditions, which is a time-consuming and expensive procedure.
It is an object of the present invention, therefore, to overcome the problems and drawbacks of known methods of abrading.